Abstract
One hundred and five mature pods from a solitary tree of Acacia coriacea subsp. pendens Gowen and Muskin growing in Botanical Garden of University of Karachi, Pakistan, were collected in the month of March 2012 and studied for various size parameters after air-drying for around two months. The pod weight averaged to 2.23 ± 0.073g (ranging from 0.9965 to 4.8622g) and tended to distribute normally. The number of mericarps per pod varied by 26.99% and averaged to 7.24 ± 0.19. The brood size averaged to 4.37 ± 0.19 seeds and tended to be positively skewed. The frequency of pods containing seed in each mericarp was low (10%). Ninety per cent of the pods had one or more empty seed chambers. The seed mass per pod varied by a quantum of 44.35% and averaged to 0.5834 ± 0.2892 g and maximally 1.2572g in one pod. The pericarp mass of pods varied from 0.4934 to 3.5002g per pod (CV: 31.6%). The weight of single seed for a sample of 399 normal seeds collected from 105 pods was less variable (15.58%) as compared to the brood size (CV: 44.35%). The weight of individual seed averaged to 139.70 ± 1.0827 mg varying from 58.4 to 243.7 mg (4.17 -fold variation). The distribution of seed weight of normal seeds was asymmetrical (negatively skewed). The proportion of pericarp to fruit (PFR) was 73.26 ± 0.899% and proportion of seeds to fruit (SFR) was 24.45± 0.816%. There was a positive linear relationship between logarithms of seed yield per pod and mass of the pod (r = 0.7878). The slope of the line (b) was 1.3766, not significantly different from 1 (t = 0.266, NS). Also, there was significant positive linear relationship between log (number of seeds per pod) and log (pod mass). The slope (b = 1.0594) of the regression was not significantly different from 1 (t = 0.495, NS). The investment in pericarp declined with increase of brood size significantly. The increase in brood size in a pod associated positively with seed mass proportion to pod mass but negatively with pericarp proportion to pod mass. The seed packaging costs for 105 pods was expressed on the basis of pericarp [g.g-1 seeds (SPC1 )] and pericarp [g per seed (SPC2 )]. The SPC1 averaged to 3.6399 ± 0.2197 g.g-1 seeds and SPC2 averaged to 0.4277 ± 0.0231 g per seed varying by 69.03 and 55.8%, respectively. On individual seed basis, seed packaging cost was 3.06 times of the average seed weight. SPC1 and SPC2 both distributed asymmetrically (positively skewed) i.e. the magnitude of the SPC was quite high in few pods - generally those yielding single seed. On an average 72.35% of the pod mass was allocated to protection and nutrition of seeds, 25.3% to seed production and 2.39% to the aril (elaiosome) for dispersal due to birds or ants.
